I have another thread asking about my fish but I was hoping with a more specific diagnosis I could get more help.

Still dark spots on my fish, the big spot on his side seems to be getting worse.
I noticed this morning that as he breathes it seems that his gills are black and maybe inflamed? I've never seen anything come out as he breathed before, but now when he does, the black tissue comes out and then goes back in. Is this ammonia poisoning? And if so, what are immediate treatments for him? Bigger tank and heater I already know.